By MATT CRENSON

                         AP Science Editor

                         For the Chiribaya, the first half of the 14th century was a golden age.

                         Fishermen pulled seafood aplenty from the Pacific. Llamas grazed in the foothills of the Andes. Irrigated fields yielded abundant
                         crops. A few decent-sized cities sprang up, ruled by people who kept everything humming along nicely.

                         Then, the mud came.

                         Sometime around 1350, torrential rains loosed a giant debris flow on the Chiribaya. The mud barreled down the Ilo River Valley at
                         70 mph, burying farms and cities up to 30 feet deep.

                         As a civilization, the Chiribaya, who lived on what is now the coast of southern Peru, were finished. But the people themselves
                         weren't gone; there were plenty of survivors.

                         So what happened to them?

                         A few years ago, archaeologists didn't really care. Their field shied away from linking human events to the natural environment,
                         partly because no reliable way existed to show that a natural event and a cultural change happened at about the same time.

                         ``When I grew up,'' says Michael Moseley, a professor at the University of Florida in Gainesville, ``environmental determinism was
                         a nasty word.''

                         But a change is afoot. Partly because of advances in reading the history of ancient climate as it's recorded in tree rings, glacial ice,
                         ocean sediments and lake deposits, archaeologists can match natural events with their cultural consequences.

                         They can see, for example, that two humans sacrificed by the Moche people were killed in A.D. 600 or 601, during torrential rains
                         that threatened their way of life, just as they would the Chiribayas 750 years later. They can see that a shift in rainfall patterns
                         coincided with the disappearance of the Anasazi from the Colorado plateau in the southwestern United States. And they can see
                         how people from Portugal to China reacted to a sudden climate shift that happened around 2200 B.C.

                         ``We hope to move closer, if it's possible, to being able to establish whether there are any cross-cultural generalities,'' says Garth
                         Bawden of the University of New Mexico.

                         Last month, at a meeting of the Society for American Archaeology in Nashville, Tenn., archaeologists discussed their new interest in
                         the aftermath of natural calamities. Though little is known about what happens after the smoke clears, the little knowledge that exists
                         is good.

                         ``People can make it through,'' University of New Mexico archaeologist Richard Reycraft says. ``They're just doing different
                         things.''

                         Reycraft's subjects, the Chiribaya, never regained their 14th-century glory. But they carried on, abandoning the muddy remains of
                         the city of Miraflores and establishing smaller settlements upriver and along the coast.

                         The Chiribaya had never lived right on the ocean before. But it appears that the people who had made their living fishing before the
                         landslide simply moved to beachfront property and continued plying their trade.

                         The Chiribaya also seem to have looked to their neighbors for guidance. Their own culture destroyed, they adopted not just the
                         pastoral economy but also the the clothing style and religion of the Estuquina people who lived on higher ground to the east.

                         The Anasazi seem to have made a similar transition. When changing rainfall patterns caused famine on the Colorado plateau, the
                         Anasazi moved south into the Rio Grande Valley, where precipitation remained dependable and irrigated agriculture was possible.

                         ``People would have been drawn to areas where farming was less risky than in the areas that they left behind,'' says Linda Cordell,
                         director of the University of Colorado Museum in Boulder.

                         In addition to modifying their way of life, the Anasazi also changed their religion, developing a new set of beliefs based on a
                         combination of their own traditions and those of their new neighbors. Kachina figures, which represent spirits of the ancestors in
                         Pueblo religions, began appearing much more frequently on pottery, rock art and other artifacts just after the Anasazi moved.

                         ``This isn't something that you see everywhere. It seems to be happening only now and then,'' Reycraft says.

                         In the steppes east of the Black Sea 4,200 years ago, for example, a sudden climate change led to something completely different.
                         As their home turned into desert, the herders of the region took to horseback and used wagons to move around. As the desert
                         landscape expanded, the herders' range grew, too.

                         Meanwhile, the herders' neighbors to the south weren't doing so well. In the Upper Euphrates Valley, the sudden dry spell made
                         irrigated agriculture impossible, driving out the Akkadian empire that had developed there over the previous 100 years.

                         ``This is a period of severe calamity and destruction,'' Harvey Weiss of Yale University says.

                         About the same time, the Old Kingdom in ancient Egypt collapsed and the city of Harappa in the Indus River Valley was
                         abandoned.

                         Yet it is important to remember, Weiss adds, that after a brief interlude, the Pharaohs resumed their rule and the Indus Valley
                         remained the seat of Indian civilization.

                         ``All of these collapses weren't adaptational failures,'' Weiss says, ``but were in fact adaptations to abrupt climate change.''